Briefly, a shock result threatened to overshadow general indifference in Glasgow towards the Olympics. France raced into a 2-0 lead against USA but were promptly overhauled by the reigning Olympic champions, who have already justified their position as the firm favourites.

An official attendance of 15,000 was given at Hampden Park – reports on Wednesday morning suggested more than double that number of free tickets had been dished out in a desperate bid to boost the crowd. Pertinently, in a city which can only be termed an Olympic "co-host" in the loosest of fashions, USA's win was achieved in entertaining fashion. Perhaps, just perhaps, vast expanses of empty seats will not be the overriding scene at Hampden Park for all Olympic fixtures.

Bad defending can trigger an entertaining spectacle, as was the case in the first half here. France defied their underdog status by racing into an early lead, which was swiftly cancelled out by a wounded USA.

"We have been there before and shown we can come back," said USA's coach, Pia Sundhage, of the early bother. "We are now a better team than we were in 2008. This was the first game so it was understandable that we start with a few nerves."

Hope Solo, the decorated USA goalkeeper, will feel she should have done better with Gaëtane Thiney's 25-yard effort. She failed to halt the shot – just as her defence had been lax in not closing Thiney down – and handed France their first goal.

That advantage was promptly doubled. This time USA's defending was even more generous as Marie-Laure Delie collected a loose ball and spanked in a fierce shot from inside the penalty area.

As Shannon Boxx limped from the field after just 17 minutes – her coach later refused to clarify the extent of that injury – this already seemed as if it may not be USA's evening.

Yet they began their salvation job through Abby Wambach. Completely, unmarked from a Megan Rapinoe corner, the 32-year-old looped a header beyond Sarah Bouhaddi. France then claimed in vain for offside when Alex Morgan levelled the scores in the 32nd minute. France's early fluency looked to have disappeared, yet Delie then spurned a fine opportunity to send them back in front before the interval.

The Hampden crowd began occasional bursts of "U-S-A". Having worked their way through the level of security which is unfortunately a prerequisite for Olympic venues, even mild mannered individuals would be of a mind to shout anyway. Levels of policing outside the stadium were noticeably high, even compared to the routine international fixtures and domestic finals which take place on Glasgow's south side.

and had further cause for celebration within 11 minutes of the restart. Carli Lloyd, the replacement for Boxx, drilled home a fine angled shot from long range. The comeback was complete.

Morgan was gifted the most simple of tasks in knocking in USA's fourth, adding gloss to what had developed into a perfectly straightforward win. In a swift counterattacking move, Tobin Heath marauded down the left flank and crossed for Wambach. The pass actually evaded everyone, allowing Morgan to score completely unchallenged at the back post.